Polyarylene sulfide resins have good mechanical strength, heat resistance, chemical resistance, moldability, and dimensional stability and due to these properties they are used in electric and electronic appliance parts, automobile parts, etc.
These parts are frequently bonded to part materials composed of epoxy resins and the like while these parts undergo secondary processing. However, polyarylene sulfide resins have relatively low adhesion to other resins, in particular, epoxy resins. Accordingly, for example, when polyarylene sulfide parts are bonded to each other or when a polyarylene sulfide resin is bonded to another material with an epoxy-based adhesive, or when sealing of electric and electronic parts is performed by using an epoxy resin, the low adhesion of the polyarylene sulfide resin to the epoxy resin (may simply be referred to as “adhesion”) has posed a problem.
Methods for improving adhesion of such part materials have been proposed, in which the surface of a molded product is mechanically or chemically roughened so that the adhesion strength is improved by an anchoring effect. Examples these methods include using a mixed solution of chromic anhydride and sulfuric acid, a solution prepared by dissolving a Friedel-Crafts reaction catalyst in an organic solvent (for example, refer to PTL 1), or a treating agent containing chlorosulfonic acid and dichloroethane (for example, refer to PTL 2). However, these methods often involve use of dangerous drug harmful to human body and have not been recognized as practical due to environmental issues related to health and safety and wastewater treatment.
Also proposed is a method for improving adhesion of a polyarylene sulfide resin to an epoxy resin, the method involving adding carnauba wax to the polyarylene sulfide resin (for example, refer to PTL 3). However, although some improvement is observed in adhesion of a polyarylene sulfide resin, the adhesion is not sufficiently high for practical application; moreover, significant deterioration of mechanical strength was observed.
To address this issue, there have been proposed methods for reducing degradation of adhesion and mechanical strength, in which an oxidized polyethylene wax serving as a releasing agent is added to a polyarylene sulfide resin composition containing a polyarylene sulfide resin and a filler so as to improve the balance between the mold releasing property and the mechanical properties of the molded product (for example, refer to PTL 4 and PTL 5). However, in these cases also, the adhesive effect of the polyarylene sulfide resin is low and insufficient for practical application.